Search a number
alternating n.  and  centered pentagonal n.

First numbers that belong to both sets:

1, 6, 16, 76, 141, 181, 276, 456, 856, 4101, 9456, 12781, 21856, 36301, 58141, 70141, 70981, 141016, 147016, 167056, 218301, 294981, 296701, 363856, 389076, 450501, 589276, 636301, 674701, 854101, 898501, 965656, 981256, 1212781, 1630141, 1634181, 1898781, 2369256, 3094141, 3274701, 3454501, 4163476, 5016181, 5238141, 5472301, 6901456, 6943056, 7254781, 7678141, 7810141, 7818981, 8367676, 9452701, 10105276, 10185856, 10707076, 10925476, 21090301, 23218141, 27830581, 32301076, 32589276, 36509656, 36969676, 38367016, 38523876, 49272901, 49650981, 52109476, 61690141, 69050701, 69076981, 69498141, 69894141, 70185256, 72105676, 76107016, 76327876, 76549056, 81810301, 87838141, 89296381, 90165076, 92583276, 94787016, 94941016, 96767656, 96923256, 107830141, 109412101, 123078181, 125298301, 127038781, 129294181, 129870141, 141056581, 141094141, 141658141, 143470501, 145294381, 181454701, 185610181, 189072781, 210749856, 218907016, 234909856, 250125016, 250525276, 250925856, 254545476, 254949256, 258343476, 274707016, 292167276, 292329456, 296507476, 296943256, 307830781, 321290581, 323050141, 327670381, 341494141, 349074181, 385858381, 414381876, 434709456, 434907276, 450341656, 472965676, 490385076, 490945456, 505272181, 507478141, 525878781, 529438141, 541070581, 549414501, 567272581, 585492781, 616107256, 632541856, 721098181, 723818101, 747230581, 761038141, 763832301, 787878141, 789210141, 789298981, 810945276, 818165476, 832701876, 852529056, 870349056, 874365256, 890145076, 892127476, 898941016, 905494981, 907018141, 925492101, 945610381, 969092581, 989676781.